Abstract: An apparatus for controlling a car of a hydraulic elevator by variable-speed-driving an electric motor directly coupled to a hydraulic pump so as to adjust the rate at which oil is supplied from the hydraulic pump to a hydraulic jack system, the apparatus having a speed controller for variable-speed-driving the electric motor, a first detector for detecting the speed of the car, a second detector for detecting the rotational speed of the electric motor, a third detector for detecting a pressure in the hydraulic jack system, a feedback circuit for returning a control signal for limiting vibration of the car as a feedback signal to the speed controller. The feedback circuit forms the control signal from a differential signal representing the difference between a car speed value converted from the rotational speed of the electric motor detected by the second detector and the car speed detected by the first detector and a pressure signal representing the pressure detected by the third detector.

Abstract: The wire cut electric discharge machining apparatus includes a tension applying device for tensing a wire electrode, an instruction signal generating device for providing a movement instruction and a tension instruction for a wire electrode, the speed detecting device for detecting an actual speed of the wire electrode, comparison circuitry for comparing the actual speed detected by the speed detecting device with an instructed speed of the movement instruction provided by the instruction signal generating device and the instruction value correcting device for correcting the tension instruction value which is provided by the instruction signal generating device according to a result of comparison of the comparison device. Hence, in the wire cut electric discharge machining apparatus, the tension of the wire electrode can be controlled with high accuracy.

Abstract: In a method of positioning a wire electrode and a workpiece relative to each other in a wire cut electric discharge machine, the wire electrode is stopped under tension, the wire electrode and the workpiece are moved relative to each other, and when the wire electrode and the workpiece are brought into contact with each other, the relative movement is stopped to detect the relative position of the wire electrode and the workpiece, whereby the wire electrode and the workpiece can be positioned relative to each other with high accuracy and reproducibility.